FIELD OF THE INVENTION
The invention relates to a method for controlling an injection of fuel in an internal combustion engine. In accordance with a driver's request (gas pedal position) and input variables including engine speed, an injection parameter is chosen for the steady state operation of the internal combustion engine.
Such a method is described in German Patent DE 195 35 056 C1 corresponding to U.S. Pat. No. 5,680,842. The start-of-injection angle (injection timing) is controlled here by of an engine control unit which, in a characteristic diagram, determines the necessary injection information, in particular the start-of-injection angle, as a function of injection variables such as the position of the accelerator pedal and engine speed, in order to operate an internal combustion engine. This is usually effected by storing the necessary injection information in a characteristic diagram for various input variables. Such a characteristic diagram is as a rule optimum for the steady-state operating condition of the internal combustion engine, since the values contained in it originate, as a rule, from engine test bed trials. For non-steady-state operating conditions, i.e. for transitions from one steady-state operating condition into another condition, the values supplied by the characteristic diagram are not optimum, in particular in terms of exhaust emission behavior and fuel consumption. From the prior art it is known to use gradients of engine operating characteristic variables plotted over time, such as the desired value of the engine torque or engine speed, for example, in order to correct the values stored in the characteristic diagram for non-steady-state operating phases in order thus to achieve improved engine operating behavior. This is effected in that for the gradients of one or more engine operating parameters plotted over time, a corresponding characteristic diagram is provided whose values for non-steady-state operating phases can be used to correct the values of the characteristic diagram for steady-state operating phases. For the additional characteristic diagram it is necessary, on the one hand, to provide a corresponding memory module and, on the other hand, it is necessary to determine the values of the characteristic diagram experimentally.
Published, Non-Prosecuted German Patent Application DE 43 06 208 A1 discloses that the correction values are allowed to decay to zero. The correction values and the decay behavior are selected by accessing operating-parameter-dependent characteristic diagrams.